A177460 Smallest k such that A000217(n)+k and A000217(n)-k are both prime.

0, 1, 3, 2, 2, 9, 5, 2, 12, 5, 5, 12, 2, 7, 27, 4, 8, 9, 13, 2, 24, 5, 7, 12, 2, 5, 27, 4, 2, 75, 19, 38, 18, 11, 7, 30, 2, 7, 9, 2, 16, 63, 7, 4, 12, 25, 5, 12, 16, 35, 51, 2, 2, 9, 13, 16, 12, 17, 41, 60, 20, 13, 51, 8, 32, 9, 5, 22, 18, 35, 19, 12, 22, 7, 75, 34, 2, 93, 11, 2, 30, 25, 11

Offset: 2

Author

Vladimir Joseph Stephan Orlovsky, May 09 2010

Keywords

• nonn

Examples

			3+-0->primes. 6+-1->primes. 10+-3->primes. 15+-2->primes,..
		

Crossrefs

Cf. A000217, A172989, A172990.

Programs

Mathematica

f[n_]:=Block[{k},If[OddQ[n],k=0,k=1];While[ !PrimeQ[n-k]||!PrimeQ[n+k], k+=2];k]; Table[f[n*(n+1)/2],{n,2,5!}]

Extensions

Definition rephrased and offset adapted by R. J. Mathar, Aug 15 2010